The mission's statement came a day after the electoral council in this Caribbean nation barred the groups, including Lavalas, the influential party of exiled former President Jean-Bertrand Aristide, who called the decision "an electoral coup d'etat."

Lavalas, which gets strong support from poor people in the capital, previously was banned from the 2006 presidential election, and it boycotted Senate run-off ballots last June after the council disqualified its candidates on a technicality.

The Lespwa movement that formed around President Rene Preval when he ran for president in 2004 was also was banned from next year's vote.

The council would say only that the 17 groups were excluded from the legislative elections because they submitted improper documents.

The U.N. mission issued a non-confrontational statement that did not mentions any groups or politicians by name, asking only that Haitian officials avoid making decisions that might hint at unequal treatment. It also requested that officials review documents from all parties with openness and equality.

At a news conference Friday, the electoral council said its decision was irreversible. It said the Department of Legal Affairs would answer questions about why some parties were excluded and 53 were authorized to participate. The department did not issue any statements Friday, and its officials could not be reached.

The U.N. mission said it would meet with all those involved to ensure free and fair legislative elections, which are now scheduled for Feb. 28 but might be postponed to coincide with a presidential ballot later next year.

The 9,000-member U.N. peacekeeping force deployed in Haiti after Aristide was ousted in a 2004 rebellion.

Legislators in the politically unstable country, one of the poorest in the Western Hemisphere, chose a new prime minister last week as tension remain high over the presence of the peacekeepers. Jean-Max Bellerive is the sixth person to hold that post since 2004.